Hello,
I've been away from the crypto scene for several years, I've discovered that i had 1 BTC+ on an old dusty HDD from back in the day.
I didn't realize there was so many new crpyto currencies, now I'm overwhelmed, I'm looking for long-term investments, i'll just put it back in the closet and forget about it for another few years.
Here's my current breakdown
20% BTC
10% LTC
10% ETH
10% NEO
10% Dash
10% XMR
So this leaves me about 30% or so left to put into smaller altcoins and that's where i'm having a hard time.
Suggestions are really welcomed

Slow down.
Look, I can't tell you how wrong your current approach is.
You made $3,000 with Bitcoin and now want to sell it for random altcoins? Doesn't make sense.
If I were you, I would simply continue holding BTC. It has worked immensely for you so far, why not keep holding?
Also, as another poster mentioned, you now have 1 Bitcoin Cash (BCC) as well. That is currently going for $250.
Why not sell your BCC to make some extra cash money, then use the $250 to buy altcoins that you desire?
This way you still get to invest in some alts, and also keep your Bitcoin.
I really didn't know about the BCC until right now, i'll read up on it, you're right, i may just keep that BTC intact and only invest that $250, i think i was just getting excited?...
I like how you weren't disappointed that it was only one Bitcoin you purchased back then and not more. When was it and how much fiat did you fork out if you remember?
I remember getting intrigued very early on around 2010 when I first downloaded and installed the core and only because I got distracted and/or found it difficult to find out how to buy Bitcoin with AUD, I gave up and forgot about it.
But to answer your question, all depends what you're prepared to risk. Low risk option is always put it on a trustworthy exchange in the funding wallet and collect interest from traders who will borrow it for margin trading.
I remember mining a little and buying? It was so cheap, <$10? You don't often find $3k in the cracks of your couch, so i was pretty happy to find even just 1 by complete accident.